1. Field of Invention
This application relates generally to material identification and more specifically to inspection systems that perform material identification.
2. Discussion of Related Art
Inspection systems are widely used to obtain information on objects that cannot be readily seen in an external examination of items under inspection. Inspection systems are used as part of security systems, such as explosive detection systems, used at airports or other settings to preclude people from smuggling explosives into a secure area by concealing them in packages. Though, inspection systems may also be used during mail processing to obtain information on objects in packages, during mail processing on bones or other structures inside a human body during medical testing, on objects in food products as part of health inspections, on minerals in ore as part of a mining operation and in many other settings.
Frequently, inspection systems use penetrating radiation, such as x-rays. The inspection system captures the radiation after it has interacted with an item under inspection. Analysis of the radiation reveals properties of objects inside the item under inspection. Based on this analysis, a security system can “clear” an item by determining that it contains only innocuous objects or can “alarm” an object by determining that it likely contains one or more objects that pose a threat. Other inspection systems may cause other actions based on the properties of the objects identified in the inspection.
In capturing radiation, some inspection systems discriminate between radiation emanating from an object at different angles. Angular discrimination may be used in conjunction with a focusing system that passes only radiation from a specific region on which data is to be collected. In some instances, controlling the measurement angle reveals information useful for analyzing an object. For example, the angle at which radiation scatters from an object is an indication of the type of material that makes up the object. As one example, x-ray diffraction analysis may be used to analyze the spectrum of radiation scattered from a region of an item under inspection to determine whether that region contains innocuous material or a threat material.